Zero—field—cooled and field—cooled magnetizations and magnetic susceptibility of itinerant ferromagnet SrRuO3

Zero-field-cooled(ZFC) magnetization,field-cooled(FC) magnetization,ac magnetic susceptibility and major hysteresis loops of itinerant ferromagnet SrRuO3 have been measured at magnetic ordering temperatures ranging from 5 to 160K.An empirical model is proposed to calculate the measured ZFC magnetization.The result indicates that the calculated ZFC magnetization compares well with the measured one.Based on the generalized Preisach model.both the ZFC and FC curves are reproduced by numerical simulations.The critical temperature and critical exponents are determined by measuring the ac magnetic susceptibility in different bias magnetic fields at temperatures in the vicinity of the point of phase transition.     

The magnetic behavior of CeB6: Comparison between elastic and inelastic neutron scattering,initial susceptibility and high-field magnetization

We report measurements of the elastic and inelastic neutron scattering, initial susceptibility and high-field magnetization on thoroughly prepared poly- and single crystalline samples of CeB₆. Part of these experiments have been performed at temperatures down to 60 mK and magnetic fields up to 70 kØe. Our neutron-diffraction data provide the first proof that CeB₆ is an antiferromagnet belowT _N2K as has been suggested by previous bulk experiments. The reduced value of the low-temperature magnetic moment both below and aboveT _N points to the existence of a Kondo effect of the ₇ crystal-field (CF) ground state of Ce³⁺. From the low-temperature width of the quasielastic neutron line, the Kondo temperature is inferred to beT _K3 K. The thermal variation of the initial susceptibility (forT>20K) is semiquantitatively explained invoking, besides the Kondo effect, a ₇- ₈ CF splitting of 70 K and magnetic interactions, which are about 10 times stronger between ₈ states than those between ₇ states. This large ₈- ₈ exchange interaction is also assumed to account for the most striking result of this work, i.e. the lack of any CF-transition peak up to 44 meV in our inelastic neutron-scattering spectra.     

Persistent currents and magnetization in two-dimensional magnetic quantum systems

Persistent currents and magnetization are considered for a two-dimensional electron (or gas of electrons) coupled to various magnetic fields. Thermodynamic formulae for the magnetization and the persistent current are established and the “classical” relationship between current and magnetization is shown to hold for systems invariant both by translation and rotation. Applications are given, including the point vortex superposed onto an homogeneous magnetic field, the quantum Hall geometry (an electric field and an homogeneous magnetic field) and the random magnetic impurity problem (a random distribution of point vortices).     

Effects of transverse field on the magnetization and initial susceptibility of a molecular-based magnet

The molecular-based magnet system consists of mixed spin-2 and spin- 5/2 honeycomb lattices with ferrimagnetic interlayer coupling. Within the framework the effective-field theory with self-spin correlations and differential operator technique, the effects of the transverse field on the magnetization and initial susceptibility have been studied in detail.     

Ferrimagnet with magnetic instability: influence of susceptibility on magnetization curves

Magnetic phase diagrams of a two-sublattice ferrimagnet with an unstable subsystem are calculated when the susceptibility is taken into account. Analytical expressions for the critical fields and characteristic values of parameters are derived. Evolution of the magnetic phase diagrams and magnetization curves is analyzed. The magnetization curves of the compounds Y_0.8Ho_0.2(Co_0.925Al_0.075)₂ and Y_0.83Er_0.17(Co_0.92Al_0.08)₂ are measured in fields up to 100 T. Two metamagnetic transitions associated with the magnetic instability of the d-subsystem are observed in both compounds. The numerical analysis in the framework of the molecular-field theory provides a determining of the reliable f–d exchange parameters.     

Effect of distributed particle magnetic moments on the magnetization of NiO nanoparticles

Magnetization of NiO nanoparticles, at different temperatures, is measured and analyzed taking into account a distribution in particle magnetic moment. We find that disregarding this distribution in the analysis is the reason for the many anomalous observations reported on this system in the literature.     

Pressure influence on remanent magnetization and anisotropy of magnetic susceptibility of synthetic magnetite and haematite

Abstract

Stress effect on remanent magnetization and anisotropy of magnetic susceptibility of synthetic samples of magnetite (Fe₃O₄) and haematite (Fe₂O₃) of submicron grain size is reported. Both the parameters were investigated under uniaxid pressure within the range of elastic deformation. All the measured parameters display significant changes of different pattern.     

AC susceptibility enhancement studies in magnetic systems

Enhancement of AC susceptibility has been observed for typical ferromagnets (Gd), reentrant spin glasses like (Fe_1.5Mn_1.5Si) and canted spin systems (Ce(Fe_0.96Al_0.04)₂). The data have been interpreted with the help of a simulation model based on dry friction-like pinning of domain walls for systems having ferromagnetic domain structures. A strong pinning mechanism appears in the reentrant spin glass like and canted spin systems at low temperatures in addition to the intrinsic one in the ferromagnetic phase. The temperature variation of the pinning potential has been given qualitatively for the reentrant spin glass like systems.     

Simultaneous, single particle, magnetization and size measurements of micron sized, magnetic particles

Single particle magnetization and size measurements of micron and nano sized, magnetic particles were made using a previously described device referred to as Cell Tracking Velocimetry, CTV. Three types of commercially available, and commonly used, magnetic particles were studied in this report. While the CTV instrument provides individual particles measurements, the average magnetization and size measurements were found to have reasonable agreements with reported values from instruments which measure bulk values. In addition, the CTV instrument, using electromagnets, can also determine magnetization curves, which also proved to have reasonable agreement with other published studies. Given that magnetic separation and analysis technology is dependent on the quality of the magnetic particles used, studies such as this one using CTV provide not only average data, but also provides information with respect to the distribution of the properties such as magnetization and size. For example, the spread of the data in magnetic and settling velocities were found to be predominately due to the size distribution of the analyzed particles.     

Dynamical magnetic susceptibility of intermediate valence Tm systems

We calculate the inelastic part of the magnetic neutron scattering cros section of a periodic model for valence fluctuations between two magnetic configurations. The calculations is restricted to the paramagnetic pahse where the coherent potential approximation is used.The resulting frequency (ω), wave vector (q) and temperature dependence agrees qualitatively with the experimental results in TmSe.We find that even for parameters for which there is no gap in the total density of states, an inelastic peak is present with a similar q dependence as the experimentally observed one.We discuss the effects of sample composition and compare the results with those corresponding to the impurity version of the model and the experimental results in dilute systems.     

Extracting anisotropy energy barrier distributions of nanomagnetic systems from magnetization/susceptibility measurements

Anisotropy barrier distributions of single domain particle systems are an important issue in the nanomagnetism and its applications. Different methods to extract the distribution from temperature, field, or time-dependent magnetization/susceptibility are reviewed and compared. A single domain particle system is measured to test the methods.     

基于永磁恒定磁场激励的起始磁化曲线测量

现有起始磁化曲线测量系统需绕制励磁线圈和感应线圈,在线应用受限.为此,本文提出了一种基于永磁恒定磁场激励的起始磁化曲线测量原理并搭建了相应测量系统.该系统采用永磁磁化器作为激励磁源,以对称磁化方法在圆柱棒状构件上激励出随轴向位置变化的恒定磁场作为激励磁场;采用阵列霍尔探头测量构件表面不同提离下的轴向和法向磁感应强度;并基于多项式外推法和磁场高斯定理外推法,推算构件与空气分界面上的轴向和法向磁感应强度;进一步地,根据分界面上的磁感应强度获取构件的起始磁化曲线.系统测量结果表明,在永磁恒定磁场激励下,无须励磁线圈和感应线圈即可方便地获取棒状构件的起始磁化曲线,测量误差小于10%,测量误差标准差小于0.01,重复性较好.该系统可为便捷地在线测量棒状构件起始磁化曲线提供新途径.     

Dynamics of magnetic stray fields at initial stage of magnetization reversal of micrometer-sized Co dots

The dynamical evolution of magnetic stray fields has been investigated at the initial stage of magnetization reversal of a microstructured cobalt film (Co dots). Quantitative measurements of the domain magnetization and of the shift of the domain boundaries have been performed at 1 ns intervals. The measurements were performed using an emission electron microscope. The photoelectrons were excited from a sample using well-defined synchrotron-radiation pulses in single bunch operation mode (UE56/1-PGM at BESSY II, Berlin). The magnetization movement was initiated by an external magnetic field pulse, the pulse width being 8 ns. The magnetic field pulse was synchronized with the synchrotron single bunch radiation pulses. The lateral and time resolutions of the applied pulses were 50 nm and 500 ps, respectively. PACS 31.70.Hq; 68.37.Xy; 75.70.-i; 75.75.+a     

Low-temperature magnetization and susceptibility of an amorphous ferromagnet

The zero temperature magnetization and susceptibility are considered for an amorphous ferromagnet in which the local anisotropy field H_A has random directions. Results are used to estimate H_A from existing data in amorphous TbFe₂.     

Temperature variations of susceptibility and magnetization for nickel

Temperature variations of paramagnetic susceptibility and the magnetization for nickel are calculated in the band model. The value of high-field susceptibility at 0 K is also estimated.     

High-field susceptibility and magnetization in Fe-Ni invar alloys

The high-field susceptibility of Fe-Ni Invar alloys does not give rise to a sudden increase at the Curie temperature. The decrease in magnetization with increasing temperature is attributed to the T² term as well as to the spin wave term for Fe-Ni Invar alloys.     

Nonreciprocal elastic scattering of unpolarized neutrons by magnetic systems with the noncoplanar magnetization distribution

It is shown that the elastic scattering of unpolarized neutrons by systems with the noncoplanar spatial magnetic induction distribution in nonreciprocal. Two systems with the noncoplanar distribution of the magnetic field are proposed and calculated, i.e., a nanoparticle with vortex magnetization and a system of three magnetic mirrors. It is shown that, under certain conditions, the nonreciprocity is rather large and can be observed experimentally.     

Time dependent magnetization of a Zn0.1Fe0.9Fe2O4 fine magnetic particle system

The time dependent magnetization measurements of the fine particles (100Å) of Zn_0.1Fe_0.9Fe₂O₄ ferrite system at 68 K are reported. The time decay of magnetization is found to be logarithmic. The time dependent co-efficient varies with the applied field and is maximum at coercive field. The value of anisotropy obtained from the variation of time dependent co-efficient with field agrees well with earlier results.     

The action-angle coordinates for particle motion in magnetic mirror systems

In this paper the problem of the possibility of determining the cyclic Hamiltonian function of a particle moving about a magnetic vessel of the mirror type is discussed. From the Hamiltonian of the typeH=H(P ₁,P ₂,P ₃,Q ₃), derived by the author in a previous paper, the Hamiltonian functionH=H(J₁,J ₂,J ₃,w ₃) was determined whereP _i ,Q _i are the generalized impulses and coordinates andJ _i ,w _k is the action-angle coordinate system. The determination of the form H=H(J₁,J ₂,J ₃) depends on the possibility of solving the quadrature of the Hamilton-Jacobi equation leading to an open form in the general case. Some approximative expressions, suitably replacing the mirror system, are discussed. The solution has been extended to the range of relativistic velocities. The question of the uniqueness of the expression of the Hamiltonian function in cyclic variables is analyzed; it follows from this that the class of canonical transformations leaving the Hamiltonian in a cyclic form does not allow any great simplification of the relatively complicated transformation expressions.